Surgery outcomes in those with neurocognitive disorders
Authors: Brendan S Silbert, David A Scott, Lisbeth A Evered
Journal: The Lancet Healthy Longevity (2023)

The prevalence of neurocognitive disorders is rapidly increasing in high-income countries as the population ages and the prevention and management of many other life-threatening diseases improves. In Australia, dementia (including Alzheimer's disease) is now the leading cause of death in females and the second leading cause of death in males. Moreover, people older than 65 years comprise 16% of the population but receive more than a third of elective surgeries.1Australian Institute of Health and WelfareDementia in Australia.https://www.aihw.gov.au/reports/dementia/dementia-in-aus/contents/aboutDate accessed: September 1, 2023Google Scholar The convergence of these two issues highlights the importance of understanding how cognitive decline might play a part in outcomes after surgery and anaesthesia. Unfortunately, perioperative studies on the effect of preoperative neurocognitive disorders on postoperative outcomes, other than further cognitive decline, are scarce. One prospective study2Robinson TN Wu DS Pointer LF Dunn CL Moss M Preoperative cognitive dysfunction is related to adverse postoperative outcomes in the elderly.J Am Coll Surg. 2012; 215 (discussion 17–18.): 12-17Crossref PubMed Scopus (178) Google Scholar screened for cognition and showed that impaired preoperative cognition is associated with poor outcomes including higher incidence of delirium, longer hospital stay, discharge institutionalisation, and 6 month mortality. Two retrospective database searches linked preoperative poor cognition to poor outcomes for hip fracture repair3Seitz DP Gill SS Gruneir A et al.Effects of dementia on postoperative outcomes of older adults with hip fractures: a population-based study.J Am Med Dir Assoc. 2014; 15: 334-341Summary Full Text Full Text PDF PubMed Scopus (76) Google Scholar and all major surgeries.4Hu CJ Liao CC Chang CC Wu CH Chen TL Postoperative adverse outcomes in surgical patients with dementia: a retrospective cohort study.World J Surg. 2012; 36: 2051-2058Crossref PubMed Scopus (82) Google Scholar Unfortunately, with the exception of delirium, much of the research into perioperative neurocognitive disorder has focused largely on further deterioration in cognition after surgery rather than generalised poor postoperative outcomes. It would be informative to have information on a link between pre-existing neurocognitive disorder and more generalised complications rather than specifically on further cognitive deterioration. Such knowledge would further underscore the imperative of preoperative screening in individuals older than 65 years as an integral part of preoperative assessment.5Crosby G Culley DJ Hyman BT Preoperative cognitive assessment of the elderly surgical patient: a call for action.Anesthesiology. 2011; 114: 1265-1268Crossref PubMed Scopus (57) Google Scholar This information would ideally be obtained by a prospective observational study in patients who were assessed for cognition preoperatively and categorised into no neurocognitive disorder or mild or major neurocognitive disorders. Subsequent long-term follow-up of outcomes would then provide data enabling an association between cognition and postoperative complications. In the absence of a prospective observational study, lower levels of evidence might provide some insight into any link between preoperative cognition and general long-term outcomes. In The Lancet Healthy Longevity, Alexander Abess and colleagues6Abess AT Deiner SG Briggs A et al.Association of neurocognitive disorders with morbidity and mortality in older adults undergoing major surgery in the USA: a retrospective, population-based, cohort study.Lancet Healthy Longev. 2023; 4: e608-e617Summary Full Text Full Text PDF Scopus (1) Google Scholar used an administrative database (US Medicare) to investigate a link between pre-existing neurocognitive disorder and mortality, discharge destination, complications, and type of surgery. The database was large, comprising more than 5·2 million individuals aged 65 years and older, 767 830 (14·59%) of whom had a pre-existing neurocognitive disorder. Abess and colleagues found that individuals with a neurocognitive disorder had higher rates of mortality at 30 days, 90 days, and 365 days after surgery compared with those without an existing neurocognitive disorder. In analysis of secondary outcomes, Abess and colleagues also found higher discharge rates to a nursing facility, and higher rates of delirium, stroke, wound infection, and urinary tract infection in those with a neurocognitive disorder compared with those without a neurocognitive disorder. These results should be taken in context. The authors acknowledge the limitations of an administrative database. Such databases are derived from information recorded by chart abstraction personnel for the purpose of billing and demographic use and differ markedly from electronic medical records or protocol-driven, prospective research data. Data might be inaccurate because of miscalculations at the administrative level, clinician misclassification, or limitations of the codes.7Boncyk CS Jelly CA Freundlich RE The blessing and the curse of the administrative database.Ann Am Thorac Soc. 2020; 17: 174-175Crossref Scopus (2) Google Scholar The authors state that Medicare claim data fail to identify dementia in about half of clinically diagnosed patients. To compensate for these missed cases, the authors have included altered mental status and unspecified signs and symptoms of cognitive function and awareness in their list of neurocognitive disorders. The Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), specifically defines mild neurocognitive disorder as a cognitive concern, modest impairment of cognition, and non-interference with daily activities, and describes major neurocognitive disorder as cognitive concern, substantial impairment of cognitive performance, and interference with daily activities. These definitions have also been applied to the perioperative period.8Evered L Silbert B Knopman DS et al.Recommendations for the nomenclature of cognitive change associated with anaesthesia and surgery—2018.Br J Anaesth. 2018; 121: 1005-1012Summary Full Text Full Text PDF PubMed Scopus (388) Google Scholar These descriptions include many individuals who would not be coded using International Classification of Diseases (ICD) codes, especially for mild neurocognitive disorders. This is acknowledged by Abess and colleagues. The authors further acknowledge that they used a list of ICD tenth revision codes, which would tend to emphasise severe neurocognitive disorders and obscure more moderate neurocognitive disorders. This is highlighted by the fact that only 156 154 (2·97%) of the population in this study had a diagnosed neurocognitive disorder according to ICD codes. This contrasts with previous estimates of individuals older than 65 years with clinical symptoms of dementia of 10%.9Manly JJ Jones RN Langa KM et al.Estimating the prevalence of dementia and mild cognitive impairment in the US: the 2016 health and retirement study harmonized cognitive assessment protocol project.JAMA Neurol. 2022; 79: 1242-1249Crossref PubMed Scopus (46) Google Scholar This does not even take into account the further 22% prevalence rate of minor neurocognitive disorder in this population,9Manly JJ Jones RN Langa KM et al.Estimating the prevalence of dementia and mild cognitive impairment in the US: the 2016 health and retirement study harmonized cognitive assessment protocol project.JAMA Neurol. 2022; 79: 1242-1249Crossref PubMed Scopus (46) Google Scholar or the high postoperative incidence of delirium.10Marcantonio ER Delirium in hospitalized older adults.N Engl J Med. 2017; 377: 1456-1466Crossref PubMed Scopus (551) Google Scholar Clearly the ICD classification in the report by Abess and colleagues has deficiencies, as it does not report a large number of individuals with neurocognitive disorder. The authors explicitly state that their use of the term neurocognitive disorder has been used liberally and does not align with the DSM-5 use of the term. It would have been appropriate for the authors to assign a more fitting term to describe their criteria for categorising ICD coding. Despite these limitations, Abess and colleagues6Abess AT Deiner SG Briggs A et al.Association of neurocognitive disorders with morbidity and mortality in older adults undergoing major surgery in the USA: a retrospective, population-based, cohort study.Lancet Healthy Longev. 2023; 4: e608-e617Summary Full Text Full Text PDF Scopus (1) Google Scholar have drawn attention to poor outcomes after anaesthesia and surgery in those with neurocognitive disorders. This is an important step to acknowledging that neurocognitive disorders must be considered as a risk factor for surgery along with other more recognised comorbidities. We declare no competing interests. Association of neurocognitive disorders with morbidity and mortality in older adults undergoing major surgery in the USA: a retrospective, population-based, cohort studyOur findings suggest that the presence of a neurocognitive disorder is independently associated with an increased risk of mortality. Identification of a neurocognitive disorder before surgery can help clinicians to better disclose risks and plan for patient care after hospital discharge. Full-Text PDF Open Access